I have 'start' and 'end' events (so, separate documents in my 'events' index) for doing work.
I don't really care about how often I start or stop; I particularly care about their difference!
Now, as a hack, I could do ugly things like using +1 for start, and -1 for end, and aggregate over the sum, but I don't want to do that.
I understand from this thread (How to find the difference of two metric aggregations in kibana) that it wasn't possible in the past. Did anything change in the mean time? Is this coming in the near future?